cpumask: Relax cpumask_any_but()

Similarly to other cpumask search functions, accept -1, and consider it as
'any CPU' hint. This helps users to avoid coding special cases.

Signed-off-by: Yury Norov [NVIDIA] <yury.norov@gmail.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: James Morse <james.morse@arm.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Fenghua Yu <fenghuay@nvidia.com>
Tested-by: James Morse <james.morse@arm.com>
Tested-by: Tony Luck <tony.luck@intel.com>
Tested-by: Fenghua Yu <fenghuay@nvidia.com>
Link: https://lore.kernel.org/20250515165855.31452-2-james.morse@arm.com

Author: YuryNorov

include/linux/cpumask.h

@@ -413,14 +413,18 @@ unsigned int cpumask_next_wrap(int n, const struct cpumask *src)
  * @cpu: the cpu to ignore.
  *
  * Often used to find any cpu but smp_processor_id() in a mask.
+ * If @cpu == -1, the function is equivalent to cpumask_any().
  * Return: >= nr_cpu_ids if no cpus set.
  */
 static __always_inline
-unsigned int cpumask_any_but(const struct cpumask *mask, unsigned int cpu)
+unsigned int cpumask_any_but(const struct cpumask *mask, int cpu)
 {
 	unsigned int i;
 
-	cpumask_check(cpu);
+	/* -1 is a legal arg here. */
+	if (cpu != -1)
+		cpumask_check(cpu);
+
 	for_each_cpu(i, mask)
 		if (i != cpu)
 			break;
@@ -433,16 +437,20 @@ unsigned int cpumask_any_but(const struct cpumask *mask, unsigned int cpu)
  * @mask2: the second input cpumask
  * @cpu: the cpu to ignore
  *
+ * If @cpu == -1, the function is equivalent to cpumask_any_and().
  * Returns >= nr_cpu_ids if no cpus set.
  */
 static __always_inline
 unsigned int cpumask_any_and_but(const struct cpumask *mask1,
 				 const struct cpumask *mask2,
-				 unsigned int cpu)
+				 int cpu)
 {
 	unsigned int i;
 
-	cpumask_check(cpu);
+	/* -1 is a legal arg here. */
+	if (cpu != -1)
+		cpumask_check(cpu);
+
 	i = cpumask_first_and(mask1, mask2);
 	if (i != cpu)
 		return i;